The present invention relates to a method of controlling the controlled system in the target position by using the direct current motor drive as a part of the driving mechanism.
The present invention especially relates to a method of the position control used for a controller to adjust a supercharged pressure of a turbo charger by controlling the opening and shutting of the passage of the intake air pipe for the turbo charger and an apparatus therefor, wherein the position of the controlled system controlled by using said motor drive mechanism is detected by an encoder.
Technology except the influence of the noise generated in the encoder when the position of the movable vane driven by the motor drive is detected with an encoder is disclosed in Japanese Patent No. 3,039512.
This method of calculation with the rotary encoder and the apparatus composed such that the signal change is not miscalculated by the noise etc. More concretely, this apparatus has a first storage means by which the signal level after the reference time has passed since the change in the output signal had been detected is memorized. Moreover, this apparatus has a second storage means by which the level of the output signal memorized in the first storage means transferred at the fixed timing is memorized.
In this apparatus, it is judged based on the levels memorized in the first and the second storage means whether to update the calculated value of the change in the output signal of the rotary encoder. Further, the signal level of the first storage means is transferred to the second storage means at the timing of the judgment end according to this judgment result.
In the above-mentioned prior art, a regular pulse and a noise are separated according to whether the pulse is detected after the rise of the signal of the encoder or during the fixed time after the rise of the signal. However, the influence of the noise cannot be completely disregarded. Especially, in a turbo control, an actual control position shifts greatly due to the accumulation of errors when the position is detected by mistake because of the noise. As a result, the controlled system does not fall in a usual dynamic range. Further, there is the possibility that the controlled system hits the stopper at a fully closed position or fully opened position, a mechanical sticking with the stopper is caused, and the gear device is damaged. Such a problem is included in the prior art.